How to Troubleshoot BACnet Communications

A common issue that users see is that a new device is added to a network but is not communicating with the segment or has intermittent communication. Troubleshoot BACnet communication problems through the following steps:

Step 1

The first troubleshooting recommendation is to lower the baud rate setting of each device on the segment to 9600. Lowering the baud rate allows slower bits per second communication and ensures that all devices on the segment are communicating at the same speed. This is accomplished by confirming all the toggles, of each device, are in the off position with the exception of MAC – 1, this toggle should be in the on position.

Step 2

In conjunction with the first troubleshooting recommendation, the second troubleshooting is that we confirm the MAC addresses of each device. During this step we’re confirming that there are no duplicate MAC addresses on the segment; if there are duplicates we will change to ensure each is independent of the other.

Step 3

In conjunction with the first and second troubleshooting recommendations, the third troubleshooting is that we confirm the device instance of each device. During this step we’re confirming that there are no duplicate device instances within the system. If there are duplicates we will change to ensure each is independent of the other. It is not required but is a best practice to have both the MAC address and device instance sequential to ensure there are no duplicates.

Step 4

With these three steps followed, put the MAC – 1 toggle in the off position of the devices and power cycle each to confirm communication is restored. This helps to reset the segment and each device will begin its search for another based on the changes made to the baud rate, MAC address and device instance.

Step 5

The system or segment may run slower than expected; this is due to the baud rate being at the lowest setting. To return the baud rate to its desired setting, put the MAC – 1 toggle in the on position of the devices, modify each devices baud rate to the desired speed. Toggle the MAC – 1 switch to the off position and power cycle each.